How much of a weight weenie are you? I have these Bontragers and love them. They are light, and I dont have any numbness issues on rides the length of which you speak of. I did a 150 miler the other day without any numbness issues, the previous year I had some numb fingers for 3 weeks:
http://www.bontrager.com/model/07025Profile designs makes a similar one that is heavier.
http://www.profile-design.com/product/aerobars/t3-plus-carbon/Dont forget your Fred bars to put them in the correct position for long distance comfort!
http://www.sirenbicycles.com/collections/allAlso, flip up elbow pads are awesome if you don't want to love out on hand positions when you aren't in aero mode. Make sure they are the correct diameter for the bars you pick.
I also really like TOGS for regular flat bars if not going to use aero bars that day:
http://togs.com/